1;2;3;4;5;6;7;8;9;10;11;12;13;14;15;16;17;18;19;20;21;22;23;24;25;26;27;28;29;30;31;32;33;34;35;36;37;38;39;40;41;42;43;44;Powderflamespraying:
Forthepowderflamesprayingprocess,powderisfeddirectlyintotheflamebyastreamofcompressedairorinertgas(argonornitrogen).Alternatively,Itisimportantthatthepowderisheatedsufficientlyasitpassesthroughtheflame.Thecarriergasfeedspowderintothecentreofanannularcombustionflamewhereitisheated.Asecondouterannulargasnozzlefeedsastreamofcompressedairaroundthecombustionflame,whichacceleratesthesprayparticlestowardsthesubstrateandfocusestheflame.
Wireflamespraying
Inthewireflamesprayingprocess,thewirefeedrateandflamesettingsmustbebalancedtoproducecontinuousmeltingofthewiretogiveafineparticulatespray.Theannularcompressedairflowatomisesandacceleratestheparticlestowardsthesubstrate.;46;47;48;49;50;51;52;53;54;55;56;Characteristicsofplasmaspraying:
Plasmasprayingproducesahighqualitycoatingbyacombinationofahightemperature,highenergyheatsource,arelativelyinertsprayingmediumandhighparticlevelocities,typically200-300m.sec-1.However,someairbecomesentrainedinthespraystreamandoxidationofthespraymaterialmayoccur.Thesurroundingatmospherealsocoolsandslowsthespraystream.Vacuumplasma(VPS)orlowpressureplasmaspraying(LPPS)reducestheseproblemsbysprayinginvacuumoralowpressure,inertgasenvironment.Plasmasprayingiswidelyappliedintheproductionofhighqualitysprayedcoatings.;58;59;Principle:
isbasicallythesameasthecombustionpowdersprayprocess(LVOF)exceptthatthisprocesshasbeendevelopedtoproduceextremelyhighsprayvelocity.ThereareanumberofHVOFgunswhichusedifferentmethodstoachievehighvelocityspraying.
OnemethodisbasicallyahighpressurewatercooledHVOFcombustionchamber